Astragalin alleviates cognitive deficits and neuronal damage in SAMP8 mice through upregulating estrogen receptor expression

Senile plaques composed of β-amyloid protein (Aβ) and neurofibrillary tangles (NFTs) composed of intracellular hyper-phosphorylated tau are major causes of cognitive impairment and neuronal damage in Alzheimer disease (AD). Astragalin (AST), a naturally-occurring flavonoid compound, was reported to have neuroprotective effects in the brain, but its effects in AD remain unknown. Herein, the learning and memory deficits were alleviated and neuronal damage in the hippocampus were inhibited after the senescence-accelerated mouse prone 8 (SAMP8) mouse were given AST (5 mg/kg or 10 mg/kg) daily by gavage for 2 months. Furthermore, AST reduced Aβ_1-40 and Aβ_1-42 deposition, decreased β-carboxyl-terminal fragment (β-CTF) protein level and tau hyper-phosphorylation, but increased α-CTF protein level and glycogen synthase kinase-3beta (GSK-3β) phosphorylation in hippocampus of SAMP8 mice. Meanwhile, the effects of AST on AD were also explored in vitro by treating primary neurons with amyloid-β1-42 oligomers (Aβ_1-42O). Consistently, AST also alleviated amyloid-β1-42 oligomers (Aβ_1-42O)-induced neuronal damage, amyloid plaques, and tau phosphorylation in vitro model. Of note, Estrogen Receptor (ER)α and ERβ expression in the hippocampus of SAMP8 mice and Aβ_1-42O-treated neurons was significantly decreased but their levels were increased by AST. Moreover, in vivo and in vitro experiments revealed that ER antagonist, Fulvestrant, reversed the effects caused by AST. Altogether, our investigation indicates that AST may ameliorate cognitive deficits and AD-type pathologies in SAMP8 mice and Aβ_1-42O-treated neurons through upregulating ERα and ERβ expression. Our findings indicate the value of AST as a potential reagent for AD treatment.